MICROSTRUCTURAL CHANGES IN Nd_2O_3 AND Dy_2O_3 DOPED Si_3N_4-TiN

摘要

The main advantage of Si_3N_4-TiN ceramics is associated with the possibility of design of ceramic composites properties that make them suitable for wide range of engineering applications. TiN dispersed in Si_3N_4 matrix improves the fracture toughness and flexural strength and with the content of TiN ranging from 20-40 vol% the resistively is less then 10~(-2) Ωm. The beneficial effect of TiN is also evident in preventing the abnormal grain growth in Si_3N_4 matrix. Both, the content of TiN and appropriate sintering aid used for liquid phase sintering of composites, have a great effect on the obtained microstructure and consequently on the final properties of composites. The optimal structure design with continuous conductive networks of fine dispersed TiN phase in a high insulating Si_3N_4 matrix is of primary importance for electroconductivity of composites. Si_3N_4-TiN is most commonly sintered in the presence of yttria as sintering aid. However the other rare earth oxides may be used to enhance the densification process and to improve the materials properties.